The present invention relates to a spacer inserted between glass plates which are stacked and rested against a pallet for storage or transport, a method for attaching the spacer to the glass plate and an apparatus for attaching the spacer to the glass plate.
Glass plates under storage or transport are usually stacked and rested against a pallet. Spacers are usually inserted between the stacked glass plates to keep the glass plates separated from each other, thereby protecting the glass plates from abrasion. Various kinds of spacers have been proposed. For example, Japanese Utility Model Publication 61-3823 discloses a spacer for packing glass plates wherein the head portion of the spacer is thicker than the glass plates, the thickness of the separating portion of the spacer is larger at its part near the head portion than at its part distant from the head portion, and the head portion is provided with a hole for passing through a fastening string.
Japanese Utility Model Laid-Open Publication 63-42638 discloses an apparatus for automatically attaching a spacer to the periphery of a glass pate. The apparatus has a support plate movable in the direction of glass plate transport, a shaft attached to the support plate to extend at right angles to the direction of glass plate transport, a swing member to swing unitedly with the shaft and a clamp member attached to the swing member to reciprocate between a position where the clamp member receives a spacer and a position where the clamp member attaches the spacer to the glass plate.
Japanese Patent Publication 56-37937 discloses an apparatus for automatically attaching a spacer to the trailing periphery of a glass plate. The apparatus has a conveyer for horizontally supporting a glass plate to convey it at a predetermined speed and a spacer conveyer disposed below the glass plate to be conveyed. The spacer conveyer is supplied with a spacer at a receiving position, runs after the glass plate at a speed faster than that of the glass plate when the glass plate is conveyed above it, and engages the spacer to the trailing periphery of the glass plate.
The spacers for packing glass plates disclosed in Japanese Utility Model Publication 61-3823 abut on each other at their head portions to prevent the fastening force of the fastening string passed through the holes in the head portions from spreading to the edges and the portions near the edges of the glass plates, prevent stress concentration from occurring at the edges of the glass plates, and thereby preventing the edges of the glass plates from damage. However, the spacer is not suitable for a robotized automated operation for loading the glass plates on the pallet and unloading the glass plates from the pallet because the fastening string must be passed through the holes in the head portions of the spacers.
Glass plates, especially those used for windows of motorcars, are often coated with decorative prints by ceramic ink, etc., at their peripheries or film-like heaters adhered to their peripheries. The glass plates, after they have gone through the printing process, advance to a bending and reinforcing process. Provided the production line of the glass plate is such that the printing process is not continuously connected to the bending and reinforcing process, the glass plates that gone through the printing process are temporarily stacked and rested against a pallet to be transferred to the bending and reinforcing process. When the glass plates are temporarily stacked and rested against a pallet, spacers are attached to the upper peripheries of the stacked glass plates to separate them from each other thereby protecting them from abrasion and damage. The spacer disclosed in Japanese Utility Model Laid-Open Publication 63-42638 has a "u" shaped cross section and is forced against the periphery of the glass plate at its open end to engage it. Thus, the spacer disclosed in Japanese Utility Model Laid-Open Publication 63-42638 may damage the film or the print adhered to the periphery of the glass plate. The space between the two opposing legs of the "u" shaped spacer decreases after a number of times of clamping by the clamp member. If the spacer is made of hard material so as to prevent deformation caused by the clamping, the spacer may damage the periphery of the glass plate.
The spacer disclosed in Japanese Patent Publication 56-37937 also has a "u" shaped cross section and is forced against the periphery of the glass plate at its open end to engage it. Thus, if the glass plate is coated with a film or a print at its periphery, the spacer may damage the film or print.